Materials Literature
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We study the dynamics of a system composed of interacting units each with a complex internal structure comprising many subunits and treat the case in which each subunit grows in a multiplicative manner. We propose a model for such systems in which the interaction among the units is treated in a mean field approximatio…
A mechanical switch in a [2]catenane, made up of a cyclobis(paraquat-p-phenylene) tetracation interlocked with a macrocyclic polyether containing a redox-active tetrathiafulvalene (TTF) unit and a 1,5-dioxynaphthalene ring system, can be thrown either chemically or electrochemically. The neutral TTF unit resides “insi…
We have measured the energy-momentum density of amorphous silicon dioxide using an $(e,2e)$ spectrometer with 20.8 keV incident, 19.6 keV scattered, and 1.2-keV ejected electron energies. The amorphous ${\mathrm{SiO}}_{2}$ sample was prepared by oxidizing a thin silicon membrane. The experimental data show a valence e…
The results of a combined study of the temperature variation of photoluminescence (PL) and dc conductivity from high optical-quality free-standing porous silicon films are presented. PL spectra of the samples have been studied in the range 10–300 K. Dc conductivity (σ) on these samples have been studied from 90 to 300…
Molecular dynamics (MD) simulation of the diffusion of water in both atactic polypropylene (aPP) and amorphous isotactic polypropylene (iPP) models has been performed. Constant particle number, constant pressure, and constant temperature (NPT) MD was employed for both systems consisting of three polypropylene chains o…
Crystal structures of turkey egg lysozyme (TEL) and human lysozyme (HL) were refined by full-matrix least-squares method using anisotropic temperature factors. The refinement converged at the conventional R-values of 0.104 (TEL) and 0.115 (HL) for reflections with Fo > 0 to the resolution of 1.12 A and 1.15 A, respect…
We have measured the temperature and frequency dependences of large (1600--2000 ppm) shifts in the ${}^{23}\mathrm{Na}$ NMR frequencies observed for sodium atoms encapsulated in silicon cages of three clathrate compounds: ${\mathrm{Na}}_{x}@{\mathrm{Si}}_{136},$ ${\mathrm{Na}}_{x}@{\mathrm{Si}}_{46},$ and $(\mathrm{N}…
Optical absorption, Stokes, and anti-Stokes photoluminescence were performed on Er3+–Yb3+ co-doped fluoroindate glasses. For compounds prepared with a fixed 2 mol % ErF3 concentration and YbF3 contents ranging from 0 to 8 mol %, important upconversion processes were observed as a function of temperature and photon exc…
We have measured low-temperature size-selective photoluminescence excitation spectra of high-quality InP quantum dots prepared by collodial chemistry. A set of samples with mean emission energies in the range from 1.9 to 2.2 eV was investigated. All samples have a size distribution of about 10%, resulting in an inhomo…
The upconversion luminescence of a ${\mathrm{Dy}}^{3+}$-doped system is presented and analyzed. ${\mathrm{CsCdBr}}_{3}:x%$ ${\mathrm{Dy}}^{3+}$ ($x=0.2,$1,5) was synthesized and grown as crystals using the Bridgman technique. ${\mathrm{Dy}}^{3+}$ ions preferentially enter this host as charge-compensated dimers. Due to…
Electron, hole, and exciton states of multishell CdS/HgS/CdS quantum-dot quantum-well nanocrystals are determined by use of a multiband theory that includes valence-band mixing, modeled with a six-band Luttinger-Kohn Hamiltonian, and nonparabolicity of the conduction band. The multiband theory correctly describes the…
The use of a column of steadily drained foam as a sample of wet foam is limited by flow instability as the liquid fraction is increased. We report a study of this instability, which takes the form of a convective roll of bubble motion at a value of liquid fraction roughly half that of the wet foam limit at which a sta…
The functionally related amidohydrolases, including D-hydantoinases, dihydropyrimidinases, allantoinases and dihydro-orotases, share a similar catalytic function of acting on the cyclic amide ring. We aligned 16 amidohydrolases by taking account of the conservative substitution and found a number of highly conserved r…
Indium tin oxide thin films consisting mainly of whiskers have been deposited on glass by electron beam evaporation. Low deposition rates (35 Å/min) and substrate temperatures in the 120–400 °C range were used. Morphology by scanning electron microscopy, crystal structure, energy dispersive analysis of x-rays, and x-r…
An experimental investigation of the in situ electrical conductivity of Wesgo Al995 polycrystalline alumina at approximately 450 °C has been performed at the high flux beam reactor at Brookhaven National Laboratory. The measured radiation induced conductivity (RIC) was about 10−8 S/m at an ionizing dose rate of 6000 G…
Considering interchain interaction and the intrachain next-nearest-neighbor hopping interaction, within the self-consistent-field Hartree–Fock approximation, we deal with two neighboring organic ferromagnetic chains. We take into account the π-electrons, the Hubbard repulsion, and antiferromagnetic correlation between…
We present evidence for a biexciton state in a molecular aggregate. Femtosecond pump-probe spectroscopy of the $H$ aggregate of an epitaxially grown trivalent metal-halogen-phthalocyanine gives distinct photoinduced absorptions to a continuum of two-exciton states and to a bound biexciton state. No signature of the bi…
Color shift and gray scale reversal for very large viewing angles are analyzed theoretically for in-plane switching. It follows that the color shift depends on the change of the effective birefringence dΔn, whereas gray scale reversal depends on the effective angle between the polarizers and the liquid-crystal directo…
The density functional theory (DFT), semiempirical molecular orbital calculations, and π-orbital axis vector (POAV) analysis are used to study the energetics and geometries of carbon nanoconic tips. The tip models are formed by introducing two to five pentagons into a graphene network corresponding to experimentally o…
First principles calculations were performed for the structural properties of superhard materials, hexagonal β-Si3N4, β-C3N4, and two model structures of β-Si2CN4 and β-SiC2N4. Bulk modulus and lattice constants a and c have been obtained by fitting the total energy calculations to the Birch equation of state. As more…